A photoacid generator generating a strong acid by irradiation of active energy ray such as light, infrared rays, electron beam or X-ray, and a chemical amplification resist where the photoacid generator is formulated into a resin component have been conventionally known and are used for several applications.
In such chemical amplification resist, the strong acid generated by the irradiation of the active energy ray acts as a catalyst to the resin component so as to change the solubility of the resin to the developing solution to form a pattern. For high sensitivity and high resolution, various resist materials have been developed, the combinations of the photoacid generators with the resins are limited. Therefore, the development of new chemical amplification resist is demanded.
The UV curing technology of a monomer and a prepolymer by the irradiation of active energy ray is classified roughly to three types of a radical type, a cationic type and an anionic type. Among them, the technique that vinyl monomers are polymerized by irradiation to photoradical polymerization initiator is the most widely developed. In addition, the technique that an acid generated by the action of light is used as cation to conduct cationic polymerization is also studied.
However, in the radical polymerization, because the polymerization is interrupted by the oxygen in the air, specific ingenuity is needed for blocking the oxygen. In the cationic polymerization, the block of the oxygen is not needed, which is more advantageous. However, the possible corrosivity and the resin modification caused by the strong acid generated from the photoacid generator remaining after curing are indicated. Therefore, it is strongly demanded that a photosensitive resin composition containing no corrosive material such as strong acid, being not inhibited by the oxygen in the air, and providing quick reaction progress in high efficiency is developed.
In view of the situations, the photosensitive resin composition containing an anionic photobase generator where the base generated by action of light is used for polymerization reactions and chemical reactions. However, the anionic photobase generator has a photosensitivity which is worse than the photosensitivity of a radical photopolymerization initiator and a cationic photoacid generator, therefore, strong activity energy ray is needed, which is disadvantageous for the anionic photobase generator.
Thus, a photobase generator capable of generating bases having high reactivity which is decomposed by irradiation is demanded. Furthermore, if an active species such as a radical in addition to a base is generated at the same time, the curing can proceed in higher efficiency.
Patent Literature 1 discloses a photosensitive resin composition containing a photoradical polymerization initiator, a photobase generator and an acrylate resin having an epoxy group. A radical and an amine occur from this photosensitive resin composition by the irradiation of the active energy ray, and the polymerization reaction of the acrylate group is induced by the radical at first, and then heating is conducted to provide the reaction of the amine and the epoxy group so as to produce the cured product.
However, the amine generated from an oxime photobase generator used in Patent Literature 1 is monofunctional, which does not work as a crosslinker for an epoxy resin. Therefore, there is a problem that in order to enhance the crosslink density of the cured product, a large amount of an acrylate having high cure shrinkage has to be added.